The field of the invention is a novel family of proteins and genes involved in development.
Cell-cell interactions play an important role in regulating cell fate decisions and pattern formation during the development of multicellular organisms. One of the evolutionarily conserved pathways that plays a central role in local cell interactions is mediated by the transmembrane receptors encoded by the Notch (N) gene of Drosophila, the lin-12 and glp-1 genes of C. elegans, and their vertebrate homologs (reviewed in Artavanis-Tsakonas, S., et al. (1995) Notch Signaling. Science 268, 225-232), collectively hereinafter referred to as NOTCH receptors. Several lines of evidence suggest that the proteolytic processing of NOTCH receptors is important for their function. For example, in addition to the full length proteins, antibodies against the intracellular domains of NOTCH receptors have detected C-terminal fragments of 100-120 kd (hereafter referred to as 100 kd fragments); see e.g. Fehon, R. G., et al. (1990). Cell 61, 523-534; Crittenden, S. L., et al. (1994). Development 120, 2901-2911; Aster. J., et al. (1994) Cold Spring Harbor Symp. Quant. Biol. 59. 125-136; Zagouras, P., et al.(1995). Proc. Natl. Acad. Sci. USA 92, 6414-6418; and Kopan, R., et al. (1996). Proc. Natl. Acad. Sci. USA 93, 1683-1688. However, the mechanism(s) of NOTCH activation have been hitherto largely unknown.
During neurogenesis, a single neural precursor is singled out from a group of equivalent cells through a lateral inhibition process in which the emerging neural precursor cell prevents its neighbors from taking on the same fate (reviewed in Simpson, P. (1990). Development 109, 509-519). Genetic studies in Drosophila have implicated a group of xe2x80x9cneurogenic genesxe2x80x9d including N in lateral inhibition. Loss-of-function mutations in any of the neurogenic genes result in hypertrophy of neural cells at the expense of epidermis (reviewed in Campos-Ortega, J. A. (1993) In: The Development of Drosophila melanogaster M. Bate and A. Martinez-Arias, eds. pp. 1091-1129. Cold Spring Harbor Press.). We disclose herein a new neurogenic gene family, kuzbanian (kuz) (Rooke, J., Pan, D. J., Xu, T. and Rubin, G. M. (1996). Science 273, 1227-1231). Members of the disclosed KUZ family of proteins are shown to belong to the recently defined ADAM family of transmembrane proteins, members of which contain both a disintegrin and metalloprotease domain (reviewed in Wolfsberg, T. G., et al. (1995). J. Cell Biol. 131, 275-278, see also Blobel, C. P., et al. (1992). Nature 356, 248-252, 1992; Yagami-Hiromasa, T., et al. (1995). Nature 377, 652-656; Black, R. A., et al. (1997). Nature 385, 729-733, 1997; and Moss, M. L., et al. (1997). Nature 385, 733-736).
We further disclose herein various engineered mutant forms of native KUZ proteins and their activities. We show that mutant KUZ proteins lacking protease activity interfere with endogenous KUZ activity and function as dominant negatives (indicating that the protease activity of native KUZ is essential to its biological functions) and that dominant negatives can perturb lateral inhibition during neurogenesis and result in the overproduction of primary neurons. We also show that proteolytic processing of NOTCH in embryos to generate the 100 kd species fails to occur in the kuz mutant embryo and expression of dominant negatives in imaginal discs or tissue culture cells blocks NOTCH processing (indicating that the primary NOTCH translation product is proteolytically cleaved by native KUZ proteins as part of the normal biosynthesis of a functional NOTCH receptor).
The invention provides methods and compositions relating to isolated KUZ polypeptides, related nucleic acids, polypeptide domains thereof having KUZ-specific structure and activity and modulators of KUZ function, particularly Notch protease activity. KUZ polypeptides, nucleic acids and modulators thereof regulate Notch signal transduction pathways and hence provide important regulators of cell function. The polypeptides may be produced recombinantly from transformed host cells from the subject KUZ polypeptide encoding nucleic acids or purified from mammalian cells. The invention provides isolated KUZ hybridization probes and primers capable of specifically hybridizing with the disclosed KUZ genes, KUZ-specific binding agents such as specific antibodies, and methods of making and using the subject compositions in diagnosis (e.g. genetic hybridization screens for KUZ transcripts), therapy (e.g. KUZ protease inhibitors to modulate Notch signal transduction) and in the biopharmaceutical industry (e.g. as immunogens, reagents for isolating additional natural kuz alleles, reagents for screening bio/chemical libraries for ligands and lead and/or pharmacologically active agents, etc.).